A two-dimensional exhaust gas nozzle for a gas turbine engine powered aircraft generally includes spaced apart stationary sidewalls with a pair of movable flap assemblies disposed therebetween, with each flap assembly including a divergent flap having a forward edge and a rearward edge. The flaps form a controllable gas exit area defined by the proximity of the flaps to each other. The forward edges define an inlet area and the rearward edges define an outlet area. The flaps are generally movable through a full range of positions, including complete sealing engagement where the gas exit area is zero. In addition, the rearward edges may be moved cooperatively to deviate the exhaust gas flow from the nozzle centerline, thereby producing vectored thrust. The two-dimensional nozzle also includes means for moving the forward edges for varying the inlet area and means for moving the rearward edges independently of the forward edges and of each other, for varying the outlet area and for vectoring the exhaust gas passing therethrough.
Two-dimensional variable area exhaust nozzles for gas turbine engine powered aircraft are well known in the art. One such exhaust nozzle is described in U.S. Pat. No. 4,375,276 to Karnarsky, comprising a plurality of primary flaps pivotally connected to a fixed structure of the exhaust nozzle and including a plurality of secondary flaps disposed downstream of the primary flaps and pivotally connected thereto. A plurality of electromechanical actuators pivotally move the flaps, with the number of actuators and flaps forming a complex and high weight exhaust gas vectoring control system.
In general, most exhaust gas nozzles utilize conventional push rod control of the flap rearward edges to provide divergence and vectoring control, requiring relatively thick sidewalls to house the linkages therein. These thick sidewalls include a thick base region which causes eddies to develop in the external airflow, substantially increasing drag. Consequently, continuing development efforts are directed at reducing nozzle weight and complexity while simultaneously reducing drag.